A hammer drill typically includes an electric motor, a hammer mechanism and/or a rotary drive. The hammer drill is powered either by an AC mains electric power supply or a battery attached to the hammer drill. A cutting tool, such as a drill bit, is supported within a tool holder mounted on the front of the hammer drill which is driven by the motor via either the rotary drive or the hammer mechanism or both to perform cutting operations. Such a hammer drill usually can operate in a hammer only mode, a drill only mode or a hammer and drill mode. EP 1 157 788 describes a typical example of such hammer drill.
During the operation of a hammer drill a large amount of dust can be generated. As such it is desirable to collect the dust for disposal. One way of achieving this is by the use of a dust extractor. EP 1 245 330 discloses an example of a dust extractor.
Dust extractors may be attached to the body of a hammer drill. The dust extractor comprises a main body and a shroud, typically mounted on the end of tubular telescoping, arm which is attached to the main body, and which surrounds the cutting tool and engages with the work piece being cut. The dust extractor comprises a dust collection box, a filter mounted within the dust collection box and an air suction device. While the hammer drill is in use, the air suction device is switched on. During use, the dust generated by the cutting tool cutting the work piece enters the shroud. The air suction device draws the air together with dust from within the shroud, through the telescoping arm into the dust collection box. The air passes then through the filter, while the dust is trapped by the filter within the dust collection box. The an air is then typically expelled from the dust extractor. Once the operation of the hammer is complete, the dust extraction box can be removed from the dust extractor and the dust removed from the dust collection box for disposal.
Some dust extractors have the air suction device located remotely from the body. For example, the cooling fan of the electric motor of the hammer drill can be used as the air suction device and generate an air vacuum source which connects to the main body of the dust extractor. The air is drawn through the filter, out of the main body of the dust extractor and then into the housing of the hammer drill where it passes through the cooling fan of the hammer drill.
In alternative designs, a fan is rotatably mounted within the main body of the dust extractor adjacent the filter. The fan is rotatably driven by a motor to generate an air vacuum source and draw air from the shroud into the dust collection box and then through the filter before expelling it from the main housing. The fan can be rotatably driven by an electric motor mounted within the main housing of the dust extractor. EP 1 459 842 discloses such a dust extractor. Alternatively, the fan can be releasably attached to the spindle of the drive motor of the hammer drill. DE4024022 discloses such a dust extractor.